Means for controlling the blast valve of a gas blast circuit breaker



wg. l5, Q? 1 W, BEATTY ET AL 3,336,454

MEANS FOR CONTROLLING THE BLAST VALVE oF A GAS BLAST CIRCUIT BREAKER Filed Dec. 29, 1964 5 Sheet$-$heet l /H/GH PRESS URE v//Qm Timm,

A T TURA/Ey ug. R5, H967 J. W. BEATTY ET AL MEANS FOR CONTROLLING THE BLAST VALVE OF A GAS BLAST CIRCUIT BREAKER Filed Deo. 29, 1964 5 Sheets-Sheet 2 HTMOSPHER/C PRESSURE /NVEA/TORS: JOHN VV. BEATTV, H/CHARD H, /W/LLER MMM 52M W w ATToR/Vfy Aug. 15, ma? J WHEAT-w ET AL 3,336,454

MEANS FOR CONTRLLING THE BLAST VALVE OF A GAS BLAST CIRCUIT BREAKER Filed Dec. 29, 1964 5 Sheets-Sheet 5 /A/ VEA/Tom: JoH/v VV. EATTV, H/o/Afw H /l//LLER, 5y MMM M ATTORNEY United States Patent Online 3,336,454 Patented Aug. 15, 1967 3,336,454 r MEANS FR CONTROLLING THE BLAST VALVE @It A GAS BLAST CIRCUIT BREAKER .lohn W. Beatty, Newtown Square, and Richard H. Miller,

Berwyn, Pa., assignors to General Electric Company, a

corporation of N ew York Filed Dec. 29, 1964, Ser. No. 421,777 Claims. (Cl. 20G-148) This invention relates to a gas blast circuit breaker and, more particularly, to improved means for controlling the blast valve of such `a circuit breaker.

In the circuit ybreaker of the present invention, there is a pair of relatively movable contacts that can be separated to draw an arc therebetween and a yblast valve that is operable .at the time of contact-separation to cause a blast of pressurized gas to flow through the arcing region to aid in extinguishing the arc. The blast valve comprises a movable valve member that can be operated from a normally-closed position toward .a fully-open position to create the gas blast. After a period of time suicient to insure extinction .of the arc, the movable blast valve member is returned to its normally-closed position to terminate the blast, thereby preventing wastage of pressurized gas that would result from continuation of the gas blast.

It is important in such a circuit breaker that the blast continue lfor a long enough period of time to insure eX- tinction of the arc. If the blast is prematurely terminated for any reason, then there is a serious danger that the arc will not be extinguished in the `desired manner.

Accordingly, an object of our invention is to provide means for insuring that the movable blast valve member remains open long enough to provide a gas blast of :adequate duration for insuring .arc-extinction.

Another object is to control the movable blast valve member with a pilot valve a'nd to provide an interlock between the pilot valve and the movable blast valve member that :acts to insure correct operation of the movable blast valve member once the pilot valve initiates opening movement of the movable blast valve member.

In carrying out our invention in one form, we provide a gas blast circuit breaker comprising a pair of contacts separable to establish an arc therebetween and blast-control means for creating a gas blast through the region of the arc to aid in extinguishing the arc. The blast-control means comprises a source of high pressure fluid and a movable blast valve member having a normally-closed position, out of which it can be moved toward a fullyopen position to create the gas blast. Actuating means is provided for the blast valve member, and this actuating means has a blast valve-opening surface on which pressurized fluid is adapted to act in a blast valve-opening direction. This actuating means is controlled by means including a pilot valve that comprises a movable pilot valve member having a normally-closed position for blocking communication between the high pressure source and the blast valve-opening surface and an open position for affording communication between the high pressure source and the blast v-alve opening surface. Means responsive to entry of the movable blast valve member into substantially its fully-open position .after the pilot valve has been opened is provided for effecting reclosing of the pilot valve when the movable blast valve member enters substantially said fully open position. Means is also provided for holding the pilot valve member open until the blast valve member enters substantially said fully-open position, thus preventing said pilot valve from closing until the movable blast valve member enters substantially its fully-open position.

In a preferred form of our invention, the blast valve actuating means has a blast valve-closing surface, and means responsive to return of the pilot valve member to its normally-closed position is provided for causing high pressure fluid to act on the blast valve-closing surface to return the movable blast valve member to its normallyclosed position upon return of the pilot valve to its normally-closed position.

For a better understanding of our invention, reference may be had to the following description taken in conjunction With the accompanying drawings, wherein:

FIG. 1 is a schematic side elevational view partly in section of a circuit breaker embodying one form of our invention.

FIG. 2 is a cross sectional view taken along the line 2-2 of FIG. 1.

FIG. 3 is a schematic cross sectional View taken along the line 3--3 of FIG. 2. FIG. 3 shows the circuit breaker in its normally-closed position.

FIG. 3a is .a schematic showing a portion of the circuit breaker when in its position of FIG. 3.

FIG. 4 is a schematic cross sectional View similar to FIG. 3 except showing the circuit breaker in a position in which its blast valve and contacts are fully-open.

Referring now to FIG. 1, the circuit breaker shown therein comprises a metallic tank 10 lled with a highly pressurized gas, preferably air. This tank 10 is mounted on a tubular insulating column 12, preferably of porcelain, that isolates the tank from ground.

Projecting into the tank 10 from opposite sides thereof are two insulating bushings 14 and 16. Each of these bushings comprises a centrally-disposed rigid conductor 1S and a tubular insulating assembly 20 surrounding and supporting the conductor 13 and insulating it from the tank 1t) when the circuit breaker is open.

At the inner end of each vof these conductors 18 is a stationary contact 22. Cooperating with their respective stationary contacts 22 are a pair of movable contacts 24, each of which is pivotally mounted rat 26 on a central metallic support 28 that is mounted on the tank 10 and electrically connected thereto. When the circuit breaker is in its closed position, as shown in FIG. 1, an electrical circuit extends through the circuit breaker via one conductor 18, one pair of contacts 22, 24 through the central metallic support 28, the other pair of contacts 22, 24, and the other conductor 18.

During a circuit-breaker-opening operation, the contacts 24 are simultaneously operated from their closed position of FIG. 1, into their open position by .driving a centrally disposed crosshead 30 in a downward direction. This crosshead 30 is coupled to the contacts 24 by means of links 32, each of which is pivotally connected at its opposite ends to a contact 24 and the crosshead 3G. When the crosshead moves downwardly from its position of FIG. 1, it acts through links 32 to pivot the movable contacts 24 about their pivots 26, moving the upper portion of each movable contact 24 toward the central support 28, thus separating the movable contacts 24 from their respective stationary contacts 22.

The above-described contact-separation produces an arc between the contacts of each pair, and this arc is extinguished after a short interval by a blast of pressurized gas which flows through the arcing region. This gas blast is produced by opening a normally-closed blast valve 35 just prior to the time the contacts separate to form the arc. The normally-closed blast valve 35 comprises a movable valve member 36 that is located in a blast passage 37. This blast passage 37 extends upwardly to atmosphere from two nozzles 38 respectively located adjacent the two arcing regions. When the movable blast Ivalve member 36 is moved in a downward opening direction from its position of FIG. 1, pressurized gas flows from the tank 10 through the nozzles 38 and blast passage 37 via paths such as illustrated by arrows 40. After the movable blast valve member 36 has remained in open position for a suflicient period to effect arc-extinction, it is returned to its closed position of FIG. 1 to terminate the gas blast. This valve-closing prevents the pressurized gas in the tank from being wasted by continued flow from the tank after a circuit-interrupting operation. The contacts are normally caused to remain open after an interrupting operation to maintain two series-related intercontact gaps in the circuit through the circuit breaker.

For controlling the movable blast member 36 and the movable contacts 24 in the above-described manner, a pneumatically-controlled operating mechanism 50 located in the hollow support 28 is provided. This operating mechanism 50 is best shown in FIG. 3. It comprises a stationary centrally-located cylinder 52 that is normally lilled with pressurized gas from the tank 10. rl`his pressurized gas is supplied from the tank through a pair of identical parallel feed passages 56, each having ports 57, 58, 59 and 59a opening into the interior of the stationary cylinder 52. The stationary cylinder 52 has a lower end wall 53 and an upper end wall 54.

Slidably mounted within the stationary cylinder 52 is a contact-opening dashpot piston 60 that is -rigidly connected to the crosshead 3i). The dashpot piston 60 has a vertically-extending piston rod 61 that extends through the lower end wall 53 and is suitably joined to a portion 150 of the crosshead 30. In this latter respect, a threaded portion of the piston rod 61 extends through the portion 150 of crosshead 30, and a nut 62 is threaded thereon to clamp the crosshead portion 150 between the nut 62 and a shoulder on the piston rod 61. Also secured to the crosshead 30 is a plurality of rods 64 that project upwardly from the crosshead :about the outside of cylinder 52. As will soon appear more clearly, contact-opening forces are transmitted through these rods 64 to effect downward opening motion of crosshead 30.

The rods 64 bear at their upper end against a blast valve actuating piston 65 that is integral with the movable blast valve member 36. This piston 65 is of an annular form and surrounds the cylinder 52 with a sliding t. A suitable O-ring seal 63 is preferably provided to prevent pressurized air from leaking past the piston 65 along the outer surface of cylinder 52. The movable blast valve member 36 is of a cylindrical form and closely surrounds the upper end wall 54, which has a circular outer periphery slidably tting within the cylindrical blast valve member 36. The outer periphery of the movable blast valve member 65 is slidably mounted within a cylindrical portion 67 of the stationary support 28. This portion 67 cooperates with a suitable piston ring on piston 65 to prevent pressurized air from leaking along this outer periphery into the space 109 beneath the piston 65.

The movable blast valve member 36 can be driven in a downward opening direction by supplying pressurized air to an act-uating chamber 66 located immediately above the blast valve actuating piston 65. In this connection, the upper end wall 54 of cylinder 52 extends radially outward past the outer periphery of the cylinder 52 and defines an upper wall for this actuating chamber 66. An inlet 69 communicates with this actuating chamber 66. When high pressure air is permitted to ow through this inlet passage 69, as will soon be described, it will flow into the actuating chamber 66 and build up a pressure that acts on the upper surface 65a of the blast valve actuating piston 65 to drive the piston 65 in a downward blast-valve opening direction. This upper surface 65a of the piston 65 is referred to hereinafter as the blast valve opening surface.

This downward movement of the blast valve piston 65 withdraws the upper sealing surface 36a of the movable blast valve member 36 from its seat, thereby producing the previously-described blast of gas along the paths 40 of FIG. l. FIG. 4 illustrates the blast valve member 36 in its fully open position with the high pressure air 4 streaming past its upper surface. Downward movement of the blast valve piston into its position of FIG. 4 is also transmitted through the rods 64 and the crosshead 30 to the movable contacts 24. This causes these contacts to open and draw a pair of arcs adjacent the nozzles 38. These arcs are extinguished after a short period by the gas blast through the nozzles.

For controlling the ow of high pressure air into the blast valve actuating chamber 66 so as to control movement of the blast valve member 36', a normally-closed pilot valve 70 comprising a moveable pilot valve member 71 is provided. Refer-ring to FIG. 3, there is a flow passage 72 located centrally of the end wall 54 and a connecting passage 73 that connects the central passage 72 with inlet passage 69. When the movable pilot valve member 71 is in its uppermost position of FIG. 3, an annular sealing surface thereon abuts against a suitable seat on the end wall 54 and thus prevents high pressure air from entering the passages 72, 73 :and 69. But when the movable pilot valve member 71 is driven in `a downward opening direction, high pressure `air is permitted to ow past the pilot valve via passages 56, 57, 72, 73, 69 into the blast-valve actuating chamber 66. thus driving the blast valve actuating piston 65 in a downward direction to efr'ect the abovedescribed opening of the blast valve ymember 36 and the movable contacts 24.

For assisting in opening the pilot valve member 71 and for holding the pilot valve mem-ber 71 in its open position for the desired period, the pilot valve member 71 is provided with a booster piston 75. This booster piston 75 is secured to the upper end of an upwardlly-extending extension of pilot valve member 71. The booster piston 75 is slidably mounted within a booster cylinder 76, and a compression spring 77 is located between the booster piston 75 and the end wall 54 to exert an upward biasing force on the movable pilot valve member 71 that normally holds the movable pilot valve member in Vlits closed position of FIG. 3. An actuating chamber 78 for the booster piston 75 is located between the upper surface 79 of the booster piston and the upper end wall of the booster cylinder 76.

The actuating chamber 78 for the booster piston is normally vented to atmosphere through `a passage 80 that extends through the extension of the movable pilot valve -member 71 into the central ow passage 72. The central how passage 72 is, in turn, normally vented to atmosphere through a passage 82 and a slot 84 formed -in the inner cylindrical surface of blast valve member 36 and aligned with passage 82 when the blast valve -is closed. When the movable pilot valve member 71 is moved in a downward direction out of its normally-closed position of FIG. 3, an enlarged portion 85 of its extension covers the entry port 86 to the passage 82, thereby blocking communication between passages 72 and 82, thus sealing the central flow passage 72 from atmosphere. Thus, when the movable pilot valve member 71 is moved in a downward opening direction, the central flow passage 72 is no longer vented to atmosphere yand high pressure air flows into the central passage 72 and through the passage 80 into the actuating chamber 78` for the booster piston. This results in a pressure buildup above the booster piston 75 that acts in a direction to drive the booster piston 75 and the movable pilot valve member 71 downwardly toward their fully-open position of FIG. 4. Y

Reset of the movable pilot valve member 71 to its closed position of FIG. 3 is accomplished at a subsequent point by supplying high pressure air to the space S7 beneath the booster piston 75. For supplying this high pressure air for resetting purposes, a pilot valve reset passage 90 is provided leading into the reset space 87. This pilot valve reset passage 90 has an inlet that is located in vertical alignment with the passage 73, but no effective communication normally is present between passages 73 and 90. However, when the movable blast valve member 36 moves into its fully-open position of FIG. 4,

an interlock slot 92 formed in its inner surface establishes effective communication between passages 73 and 90. This permits high pressure air to flow through passages 73 and 90 via interlock slot 92 and into the reset space 87, thereby ybuilding up a pressure in the reset space 87. This pressure acts in an upward direction on the lower surface 75b of booster piston 75. (Note that lower surface 7511 includes upper and lower area portions as designated in FIG. 3.) Since force on the lower surface 75b of the booster piston 75 acts in a direction to close the pilot valve 71, then surface 75b will be referred to hereinafter as the pilot valve-closing surface. Since piston 75 has a substantially larger lower surface 75l) than upper surface 79, there is a net force on the piston 75 acting in a direction to return the movable pilot valve member 71 from its position of FIG. 4 to its normally-closed position of FIG. 3. The compression spring 77 also helps to provide force for this resetting operation. The space immediately surrounding the cup-shaped booster piston 75 is vented to atmosphere through a passage 93 to prevent air from leaking between opposite sides of the booster piston along the outer :surface of the piston.

For initiating opening of the movable pilot valve member 71, a pair of pistons 100 and 102 are provided, slidably mounted in the cylinder 52. The upper piston 100, which will be referred to as the pilot piston, is directly connected to the movable pilot valve member 71. The other piston 102, `which will be referred to as the control piston, is connected to an operating rod 104 which eX- tends through an opening in the lower wall 53 of the cylinder 52 and then, as shown in FIG. 1, through a sealed opening in the wall of tank and then through the interior of the insulating support column 12. Suitable operating means (not shown) is provided at the lower end of the rod 104 for operating the rod 104 in a downward direction. As will soon appear more clearly, downward movement of the rod produces opening of the circuit breaker, and upward movement of the rod from its open position produces closing of the circuit breaker. The rod 104 preferably passes through the lower end wall 53 of cylinder 52 via a central bore 107 in the dashpot piston rod 61.

When the circuit breaker is in its closed position of FIG. '3, high pressure air is present adjacent `both the upper and lower surfaces of both of the two pistons 100 and 102. This follows from the fact that high pressure feed line 56 communicates via ports 57 and 58 with the interior of cylinder 52.

When the operating rod 104 is driven downwardly to pull the piston 102 in a downward direction, the volume 105 between the two pistons quickly increases, producing a sudden drop in pressure in this volume. This drop in pressure permits the high pressure air immediately above piston 100 to develop a large downward force that drives the pilot piston 100 downwardly in follow-up relationship to the lower piston 102. This downward motion of pilot piston 100 opens the pilot valve and thus begins movement of the blast valve member 36- and the contacts 24 toward their respective open positions, as described hereinabove.

The upper piston 100 continues moving in pneumatically coupled follow-up relationship to the lower piston 102 until the lower piston crosses the port 58. When this occurs, high pressure air ows through the port 58 into the space 105 between the two pistons, equalizing the pressure on opposite sides of the upper piston 100 to, in effect, break the pneumatic coupling between the two pistons 100 and 102.

But despite this uncoupling of the two pistons 100 and 102, the upper piston does not immediately return to its normal position of FIG. 3. This is the case because the booster chamber 78 has then filled with high pressure air acting in a downward direction on thebooster piston 75 and the movable pilot valve member 71. The downward force exerted by this high pressure air holds the pilot valve member 71 in its fully open position until the movable blast valve member 36 has reached substantially its fully open position.

When the movable blast valve member 36 does reach substantially its fully open position of FIG. 4, its interlock slot 92 establishes communication between passages 73 and 90, as previously described. High pressure air then Hows through 73 and 90 via slot 92 and soon builds up a high pressure in the pilot valve reset space 87. The rate at which this pressure buildup occurs is controlled by a manually-adjustable throttle valve 108 located in the passage 90. When the pressure in the pilot valve reset chamber 87 has built up to a predetermined level, a sufficient upward force is exerted on the booster piston 75 to return the movable pilot valve member 71 to its normally-closed position of FIG. 3.

The movable blast valve member 36 remains in its fully-open position of FIG. 4 until the movable pilot valve member 71 has returned to substantially its normally-closed position of FIG. 3. The force for blast-valve closing is developed in a blast-valve closing chamber 109 at the lower side of the blast-valve piston 65. As will soon be explained, this chamber 109 is normally vented to atmosphere. But when the pilot valve member 71 returns to its closed position while the blast valve member 36 is in its fully-open position of FIG. 4, chamber 109 is no longer vented to atmosphere and a pressureequalizing passageway is present connecting blast-valve actuating chamber 66 and the blast-valve closing chamber 109 at the lower side of the blast valve piston 65. This pressure-equalizing passageway is constituted by passages 69, 73, 72, 86, 82 and 110 and is open when the movable pilot valve member 71, 85 uncovers port 86 near the end of its above-described closing motion. Passage normally vents the blast valve closing space 109 to atmosphere through passages 82 and 84, as seen in FIG. 3. But when the blast valve member 36 is in its fully open position of FIG. 4, passage 02 is shut off from atmosphere by reason of slot 84 in the movable blast valve member moving out of alignment therewith. When the pilot valve closes and high pressure air flows from the blast-valve actuating chamber 66 to the closing chamber 109 at the lower side of the blast valve piston 65 through the above-described equalizing passage, the pressures on opposite sides of the blast valve piston 65 equalize. It will be apparent from FIGS. 3 and 4 that the blast valve piston has a larger area exposed to pressure in chamber 109 than to pressure in chamber 66. Accordingly, there is then a net force acting in an upward direction on the blast Valve piston 65, and this force acts to return the movable blast valve member 36 to its closed position of FIG. 3.

In order to prevent any substantial build-up of pressure in the blast valve closing chamber 109 while the pilot valve member 71 is in its open position (FIG. 4), a vent passage in the form of an external groove is provided in the movable pilot valve member 71. This vent passage 115 vents the passages 110 and 82 to atmosphere through a vent 116 in the end cap 54 aligned with the vent passage 115 while the movable pilot valve member 71 is in its open position of FIG. 4. This venting means 115, 116 insures that any leakage of high pressure air into blast valve closing chamber 109 (when the blast valve is open and vent 04 in the blast valve member 36 is therefore unavailable) will not build up a significant pressure in chamber 109. Preventing such pressure buildup assures that closing of the movable blast valve member 36 will not be initiated until the pilot valve member 71 has returned to nearly its fully closed position of FIG. 3.

The rate at which pressure is built up in blast valve closing space 109 can be controlled by a needle valve 120 that can be adjusted to control the rate of flow through the pressure equalizing passages 69, 73, 72, 86, 82, 110.

When the blast valve member 36 is in its closed position, illustrated in FIG. 3, it has a larger area exposed to pressure acting in a closing direction than in an opening direction, and this results in a force normally holding the blast valve member 36 closed. To assure that the `blast valve member 36 remains closed even though there might be a large drop in tank pressure or no tank pressure at all, a plurality of light compression springs 119, shown in FIG. 2, are provided in the chamber 109 beneath the blast valve piston. These springs 119 act in an upward direction against the blast valve piston 65 to resist downward opening movement of the blast valve member 36.

When the movable blast valve member 36 closes, as hereinabove described, in response to prior pilot valve closing, all the chambers upstream from the sealing surface of the pilot valve member 71 are vented to atmosphere. The manner in which such venting takes place can best be seen in FIG. 3, where both the pilot valve member 71 and blast member 36 are shown in their respective closed positions. Referring to FIG. 3, it will be apparent that the blast valve closing chamber 109 is vented to atmosphere through passages 110, S2, and 84; whereas the blast valve actuating chamber 66 is vented to atmosphere through passages 69, 73, 72, 82 and 84. The booster piston actuating chamber 78 is Vented to atmosphere through passages 80, 82 and S4. The pilot valve reset chamber 87 is vented through small :bleed passages 123 and 124 communiicating with passage 80 and then through passages 82 and 84. Venting of these chambers at -this time serves the desirable function of assuring that on a subsequent operation, p-ressures will be built up in these chambers from the same reference level, i.e. atmospheric pressure. This helps to assure that the blast valve and contact opening times will not vary appreciably from -one opening operation to the next. Also venting the blast valve closing chamber 109 assures that therewill be no pressure in this chamber acting downwardly on'the ends of rods 64 to interfere with a subsequent circuit breakerclosing operation, when the rods 64 move upwardly through chamber 109, as will soon be described.

The passages 123 and 124 leading into pilot valve reset chamber 87 function as a portion of a pneumatic lock for holding the pilot valve closed during the period between return of the pilot Valve to its closed position and return of the blast valve member 36 -to its closed position. More specifically, these passages 123, 124 assure that the pilot valve will not be opened unintentionally by any pressure differential developing on opposite sides of the booster piston 75 while the blast valve member 36 is open and booster chamber '78 is therefore unvented. In this regard, these passages 123, 124 maintain communication between chambers 78 and S7 on opposite sides of the booser piston 75 while the pilot valve is in closed position. Thus, any high pressure present in booster piston actuating chamber 78 will also be present in the reset chamber 87, and there will be a net force on booster piston 75 acting in a pilot valve-closing direction to hold the pilot valve closed in view of the relatively large closing `area 75b as compared to opening `area 79.

On an opening operation, the high pressure air that flows through passage 80 will flow almost entirely into the booster piston actuating chamber 78, with little entering the reset chamber 87 through passages 123, 124. This is the case because passage 123 is a small bleed passage and, due to its small size, does not permit much high pressure to flow into chamber 87 during the brief period before the passage 123 is covered by an Venlarged portion 126 on movable pilot valve member 71. Near the end of a pilot valve-opening stroke, this enlarged portion 126 acts as a dash-pot piston in a cylinder 12,7. Air displaced from cylinder 127 by piston 126 is forced through passage 124 which becomes progressively more restricted as the pilot valve member 71 reaches the end of its opening stroke.

After the crosshead 30 as been driven downwardly by the blast valve-actuating piston 65 to open the contacts 24, as described hereinabove, the crosshead 30 is latched in its open position by a mechanical latch shown in FIG. 4. This latch 130 holds the crosshead 30' and the interconnected contact 24 in their open positions of FIG. 4 despite the above-described return of the blast valve member 36 to its closed position. In this connection, a suitable roller 132 carried by the crosshead 30 normally holds the latch 130 in a released position. FIG. 3a shows the position of these parts when the circuit breaker is closed. When the circuit breaker is operated toward open position and the roller 132 moves downwardly past the lower end of latch 130, a reset spring 134 drives the latch clockwise about its stationary pivot 135 against the stop 136. The latch is then in its latching movement of of FIG. 4, where it can prevent upward movement of the crosshead 30 through interference with roller 132, 4thus holding the contacts open.

The control piston 102 that was moved downwardly to initiate pilot valve-opening is similarly held in its lowermost position of FIG. 4 by a suitable latch schematically depicted at 140. A reset spring 142 acts on rod 104 to bias the control piston 102 upwardly toward its initial position of FIG. 2, but the latch retains the control piston 102 in its lowermost position so long as it is desired to hold the circuit breaker open.

When the crosshead 30 moved downwardly during opening, it carried the piston 60 therewith. During most of the downward opening movement, air ahead of piston 60 was freely expelled through ythe large passage 59 in the cylinder 52 and did not substantially retard the piston 60 and crosshead 30.

Closing of the circuit breaker is effected by suitably tripping the latch 140, as by energizing .a solenoid 144. When the solenoid responds by driving its plunger to the right against a latch reset spring 145, the mainspring 142 drives the rod 104 and piston 102 upwardly. After a predetermined amount of such upward movement of rod 104, the contact-restraining latch 130 is tripped (through a linkage, not shown, that interconnects rod 104 and the lat-ch 130). Tripping of the latch 130 allows the high pressure air acting on Ithe crosshead structure 30, 64 to drive the crosshead 30 upwardly, thereby pivoting the movable contact 24 of FIG. 4 in a counterclockwise direction about stationary pivot 26 to effect circuit breakerclosing. There is `an upwardly-acting pneumatic bias on the crosshead 30 because the rods 64 extended into the vented chamber 109 and therefore had no high pressure air acting `downwardly on them. There is thus a larger area of the crosshead structure 30, 64 exposed to pressure acting .in an upward closing direction than to pressure acting in a downward direction.

The contact-closing speed is controlled by piston attached to the crosshead 30. This piston 150 is slidably mounted in a stationary cylinder 152 having a large opening 154 therein. Initial closing motion takes place at high speed Isince the air in cylinder 152 ahead of the upwardly moving piston 150 can be freely expelled through opening 154. But when the upwardly moving piston 150 passes the opening, the air ahead of it is forced through a restricted passage 156 at a controlled rate, thus providing a dashpot action that smoothly terminates upward closing movement of the piston 150 and the connected contacts. To prevent retarding low pressure from being developed above piston 150 during downward opening movement, a passage 157 containing a check valve 158 is provided in the piston to allow air to ow upwardly into the space above the piston should a reduced pressure be developed in this space.

To prevent a retarding low pressure from being developed behind the opening dashpot piston 60 during closing, a passageway 160 is provided leading from the high pressure tank into the cylinder space behind the piston 60. A check valve 162 in this passage 160 allows air to flow upwardly therethrough into the space behind the piston 60 as it moves upwardly. This check valve prevents air from flowing through passage 160 during an opening operation.

When the control piston 102 moves upwardly during the above-described closing action, the high pressure air in cylinder 52 ahead of the piston 102 is expelled first through the port 58 and then through the check valves 148, 149 in the pistons 100 and 102, respectively. At the end of the upward stroke there is high pressure air on both sides of each of the two pistons 100 and 102. Although one check valve has been shown in each piston 100, 102, we preferably use several in each piston to permit a freer flow of air from the space between the pistons during closing. The position of the parts at the end of the closing operation is depicted in FIG. 3.

A special advantage of our blast valve control arrangement is that it enables the amount of air consumed by each interrupting operation to be easily adjusted. This air consumption depends upon the length of time that the movable blast valve member 36 is open during an interrupting operation. We can easily control this period of time by adjusting the needle valve 108. This adjustment of needle valve 108 varies the time elapsing between entry of the movable blast valve into its fully open position of FIG. 4 and the instant at which it begins to return to its closed position (since such adjustment controls the rate at which the pilot valve member 71 recloses, and blast valve-reclosing cannot begin until the pilot valve is almost fully reclosed, as was explained hereinabove). This adjustment of needle valve 108 does not significantly affect the speed at which the blast valve member 36 moves during reclosing but only the length of the time that the blast valve member remains in its fully open position. Thus, we are able to select an ideal blast valve-closing speed (by suitably adjusting the other needle valve 120) and to maintain this ideal speed unchanged despite changes in the time the blast valve remains open. It will be noted that the upper ends of the two needle valves 108 and 120 are exposed to atmosphere, and an operator has ready access to them from the top of the circuit breaker without any need for entering the pressurized tank 12. By consulting the usual tank pressure gage (not shown) before and after a given opening operation, he can easily determine the extent to which adjustments of the needle valve 108 have affected air consumption.

While we have shown and described a particular embodiment of our invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from our invention in its broader aspects; and we, therefore, intend in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of our invention.

' What we claim as new and desire to secure by Letters Patent of the United States is:

1. In a gas blast circuit breaker comprising a pair of contacts separable to establish an arc therebetween and blast-control means for creating a gas blast through the region of the arc to aid in extinguishing the arc, said blastcontrol means comprising:

(a) a source of high pressure fluid,

(b) a movable blast valve member having a normallyclosed position and being movable from said normally-closed position toward a fully-open position to create said gas blast,

(c) actuating means for said blast valve member having a blast valve opening surface on which pressurized liuid is adapted to act in a blast valve-opening direction,

(d) means comprising a pilot valve for controlling said actuating means for said blast valve member,

(e) said pilot valve comprising a movable pilot valve member having a normally-closed position for blocking communication between said high pressure source and said blast valve opening surface and an open position for affording communication between said high pressure source and said blast valve opening surface,

(f) an actuating element for said movable pilot Valve member having a pilot valve-closing surface on which high pressure fluid is adapted to act in a direction to close said pilot valve member after opening movement thereof,

(g) means responsive to entry of said movable blast valve member into substantially its fully-open position after said pilot valve has been opened for establishing communication between said high pressure source and said pilot valve-closing surface thereby to effect reclosing of said pilot valve when said movable blast valve member enters substantially said fullyopen position,

(h) and means for holding said movable pilot Valve member open until said movable blast valve member enters substantially said fully-open position.

2. The combination of claim 1 in which said communication between said high pressure source and said pilot valve closing surface is established through a predetermined passageway when said movable blast valve members enter substantially its fully open position, and in which adjustable flow control means is provided in said passageway to control the rate at which pressure builds up on said pilot valve-closing surface.

3. The circuit breaker of claim 2 in combination with a housing for high pressure fluid in which said blast-control means is located, and said adjustable flow control means having a portion extending between the inside and outside of said housing to permit adjustments thereof to be made from outside said high pressure housing Without entering said housing.

4. The circuit breaker of claim 1 in combination with means responsive to return of said pilot valve member to its normally-closed position for returning said blast Valve member to its normally-closed position.

5. The combination of claim 1 in which said means for holding said pilot valve member open comprises an opening surface on the actuating element for said pilot valve member and means for supplying high pressure fluid to said opening surface when said pilot valve member is moved toward open position.

6. The circuit breaker of claim 5 in combination with means responsive to return of said pilot valve member to its normally-closed position for returning said blast valve member to its normally closed position, and pneumatic lock means for holding said pilot valve member in its normally-closed position until said blast valve members returns to its normally closed position, said pneumatic lock means ycomprising means affording communication between said pilot valve closing surface and said pilot valve opening surface when said pilot valve is closed, said pilot valve closing surface having a larger effective area than said pilot valve opening surface.

7. In a gas blast circuit breaker comprising a pair of contacts separable to establish an are therebetween and blast-control means for creating a gas blast through the region of the arc to aid in extinguishing the arc, said blast-control means comprising:

(a) a source of high pressure Huid,

(b) a movable blast valve member having a normallyclosed position and being movable from said normally-closed position toward a fully-open position to create sa-id gas blast,

(c) actuating means for said blast valve member having a blast valve opening surface on which pressurized duid is adapted to act in a blast valve-opening direction,

(d) means comprising a pilot valve for controlling said actuating means for said blast valve member,

(e) said pilot valve comprising a movable pilot valve member having a normally-closed position for blocking communication between said high pressure source and said blast valve opening surface and an open Il position for affording communication between said high pressure source and said blast valve opening surface,

(f) means responsive to entry of said movable blast valve member into substantially its fully open position after said pilot valve has been opened for effecting reclosing of said pilot valve when said movable blast valve enters substantially said fully open position,

(g) and means for holding said pilot valve member open until said movable blast valve Imember enters substantially said fully open position.

8. In the combination of claim 7:

(a) said actuating means for said blast valve member having a blast valve-closing surface on which pressurized iluid is adapted to act in a blast valve-closing direction;

(b) means for maintaining the pressure on said blast valve-closing surface at a relatively low level while said pilot valve is open;

(c) and means responsive to return of said pilot valve to its normally-closed position for causing high pressure uid to act on said blast valve-closing surface to return said movable blast valve member to its normally-closed position.

9. The circuit breaker of claim 7 in combination with means responsive to return of said pilot valve to its normally-closed position for returning said blast valve member to its normally-closed position.

10. The circuit breaker of claim 9 in combination with:

(a) `a housing for high pressure fluid in which said blast-control means is located,

(b) adjustable means for controlling the rate at which said pilot valve recloses after entry of said blast valve member into said fully open position,

(c) said adjustable means having -a portion extending from a point inside said lhousing to a point outside said housing to permit adjustments thereof to be effected from outside said high pressure housing Without entering said housing.

11. In the combination of claim 7:

(a) said actuating means for said blast valve member having a blast valve closing surface on which pressurized fluid is adapted to act in a blast valve closing direction;

(b) means for maintaining the pressure on said blast valve closing surface at a -relatively low level while said pilot valve is open;

(c) means responsive to return of said pilot valve to its normally-closed position for causing high pressure iluid to act on said blast valve closing surface to return said movable blast valve member to its normally-closed position;

(d) and adjustable flow control means for controlling the rate at which pressure builds up on said blast valve closing surface after said pilot valve has returned to its normally closed position.

Y 12. In the combination of claim 7:

(a) said `actuating means for said blast valve member having a blast valve closing surface on which pressurized fluid is adapted to act in a blast valve closing direction;

(b) means for maintaining the pressure on said blast valve closing surface at a relatively low level While said pilot valve is open;

(c) means responsive to return of said pilot Valve to its normally-closed position for causing high pressure fluid to act on said blast valve closing surface to return said movable blast valve member to its normally-closed position;

(d) and venting means responsive to entry of said movable blast valve member into substantially its normally closed position for venting said blast valve opening surface to a low pressure region.

13. In the combination of claim 7:

(a) said actuating means for said blast valve member having a blast valve closing surface on which pressurized fluid is adapted to act in a blast valve closing direction;

(b) means for maintaining the pressure on said blast valve closing surface at a relatively low level while said pilot valve is open;

(c) means responsive to return of said pilot valve to its normally-closed position for causing high pressure uid to act on said blast valve closing surface to return said movable blast valve member to its normally-closed position;

(d) and venting means responsive to entry of said movable blast valve member into substantially its normally closed position for venting said blast valve opening surface and said blast valve closing surface to a low pressure region.

14. In a gas blast circuit breaker comprising a pair of contacts separable to establish an arc therebetween and blast-control means for creating a gas blast through the region of the arc to aid in extinguishing the arc, said blast-control means comprising:

(a) a source of high pressure fluid, Y

(b) a movable blast valve member having a normallyclosed position and being movable from said normally-closed position toward a fully-open position to create said gas blast,

(c) actuating means for said blast valve member having a blast valve opening surface on which pressurized fluid is adapted to act in a blast valve-opening direction,

(d) means comprising a pilot valve for controlling said `actuating means for said blast valve member,

(e) said pilot valve comprising a movable pilot valve member having a normally-closed position for blocking communication between said high pressure source and said blast valve opening surface and an open position for affording communication between said high pressure source and said blast valve opening surface,

(f) pilot valve control means operable when coupled to said pilot valve member for actuating said pilot valve member in an opening direction,

(g) means for releasably coupling said pilot valve member to said pilot valve control means,

(h) means for releasing the coupling between said pilot valve member and said pilot valve control means when said pilot valve member has reached an open position,

(i) means for holding said pilot valve member open after release of said coupling and until said movable blast valve member'enters substantially said fullyopen position and (j) means responsive to entry of said movable blast valve member into substantially said fully-open position for effecting -reclosing of said pilot valve.

15. The circuit breaker of claim 14 in combination with means responsive to return of said pilot valve member to its normally closed position for returning said blast valve member to its normally closed position.

References Cited UNITED STATES PATENTS 2,783,337 2/1957 Beatty et al. 20G-148 2,783,338 2/1957 Beatty 200-148 3,214,540 10/ 1965 Schrameck et al 20G-148 ROBERT K. SCHAEFER, Primary Examiner.

ROBERT S. MACON, Examiner. 

1. IN A GAS BLAST CIRCUIT BREAKER COMPRISING A PAIR OF CONTACTS SEPARABLE TO ESTABLISH AN ARC THEREBETWEEN AND BLAST-CONTROL MEANS FOR CREATING A GAS BLAST THROUGH THE REGION OF THE ARC TO AID IN EXTINGUISHING THE ARC, SAID BLASTCONTROL MEANS COMPRISING: (A) A SOURCE OF HIGH PRESSURE FLUID, (B) A MOVABLE BLAST VALVE MEMBER HAVING A NORMALLYCLOSED POSITION AND BEING MOVABLE FROM SAID NORMALLY-CLOSED POSITION TOWARD A FULLY-OPEN POSITION TO CREATE SAID GAS BLAST, (C) ACTUATING MEANS FOR SAID BLAST VALVE MEMBER HAVING A BLAST VALVE OPENING SURFACE ON WHICH PRESSURIZED FLUID IS ADAPTED TO ACT IN A BLAST VALVE-OPENING DIRECTION, (D) MEANS COMPRISING A PILOT VALVE FOR CONTROLLING SAID ACTUATING MEANS FOR SAID BLAST VALVE MEMBER, (E) SAID PILOT VALVE COMPRISING A MOVABLE PILOT VALVE MEMBER HAVING A NORMALLY-CLOSED POSITION FOR BLOCKING COMMUNICATION BETWEEN SAID HIGH PRESSURE SOURCE AND SAID BLAST VALVE OPENING SURFACE AND AN OPEN POSITION FOR AFFORDING COMMUNICATION BETWEEN SAID HIGH PRESSURE SOURCE AND SAID BLAST VALVE OPENING SURFACE, (F) AN ACTUATING ELEMENT FOR SAID MOVABLE PILOT VALVE MEMBER HAVING A PILOT VALVE-CLOSING SURFACE ON WHICH HIGH PRESSURE FLUID IS ADAPTED TO ACT IN A DIRECTION TO CLOSE SAID PILOT VALVE MEMBER AFTER OPENING MOVEMENT THEREOF, (G) MEANS RESPONSIVE TO ENTRY OF SAID MOVABLE BLAST VALVE MEMBER INTO SUBSTANTIALLY ITS FULLY-OPEN POSITION AFTER SAID PILOT VALVE HAS BEEN OPENED FOR ESTABLISHING COMMUNICATION BETWEEN SAID HIGH PRESSURE SOURCE AND SAID PILOT VALVE-CLOSING SURFACE THEREBY TO EFFECT RECLOSING OF SAID PILOT VALVE WHEN SAID MOVABLE BLAST VALVE MEMBER ENTERS SUBSTANTIALLY SAID FULLYOPEN POSITION, (H) AND MEANS FOR HOLDING SAID MOVABLE PILOT VALVE MEMBER OPEN UNTIL SAID MOVABLE BLAST VALVE MEMBER ENTERS SUBSTANTIALLY SAID FULLY-OPEN POSITION. 